[Openstack] sdn multisite???

Hello All, is there any sdn solution for openstack multi site sdn ? I read something about network to network api extension for neutron presented in an openstack summit but it seems no more adopted. Any help, please? We have 3 separated openstack installations and I wonder if there is some solution for controlling network (vxlan to vxlan connection, sec groups airchestration and so on) Openstack cascading seems only a dream. Ignazio